Relay type free piston well pump



Jan. 28, 1958 D. G. KNOX RELAY TYPE FREE PISTON WELL PUMP 6 Sheets-Sheet 1 Filed June 20, 1955 Jan. 28, 958 D. G. KNOX 2,821,142 v RELAY TYPE FREE PISTON WELL PUMP Filed June 20, 1955 6 Sheets-Sheet 2 N 'h E E@ @0A/4Z@ 6. ZA/0X .INI/EN TOR.

Jan. 28, 1958 D. G. KNOX RELAY TYPE FREE PIsToN WELL PUMP 'Filed June 20, 1955 Jam 28, 1958 DKG. KNox RELAY' TYPE FREE PIsToN WELL PUMP 6 Sheets-Sheet 4 Filed June 20, 1955 Iln I'v Y amr? i953 D. G. KNOX RELAY TYPE FREE PIsToN WELL PUMP 6 She 'its-Sheet 5 Filed June 2o; 1955 Y L 5 VAR uw 0m M N Z E KV 0 4 5 w @m W L L 0 W. LLI l .d\\\\l L LL L L L wxfmv: L .www r ...-1, L l .112| LL YEL iL L a E@ 3g/@L w. 9, M Z/ M Z E WN@ w@ Z /y 2 RELAY TYPE FREE PSTDN WELL PUIVIP Application .lune 20, 1955, Serial No. 516,697

14 Claims. (Cl. 10S-52) This invention relates to free piston pump apparatus for raising oil or other fluid from wells.

In my prior Patent No. 2,676,547 granted April 27, 1954 there is disclosed a multiple free piston well pump device employing more than one plunger in a single eduction tube. In the device of that patent a stationary barrier device denes the upper limit of movement of a lower plunger and the lower limit of movement of an upper plunger. The plungers move simultaneously but each travels in its own portion of the eduction tube.

in accordance with my present invention I eliminate the barrier device and provide two or more plungers which travel freely within the same eduction tube. The plungers each have a passageway extending axially therethrough and a valve for closing the passageway. When a descending plunger meets an ascending plunger in the same eduction tube, the load of well fluid carried above the lower ascending plunger passes through the passageway in the upper descending plunger. Contact between the plungers acts to open the valve in the lower plunger and close the valve in the upper plunger, thereby transferring the load of well iluid to the upper plunger, The plungers each reverse direction; the upper plunger raises the load of well uid while the lower plunger drops back down the eduction tube. The contact between the plungers and the transfer of the load of well fluid takes place at a location which may be approximately midway of the extremes of travel of the two plungers, but the location is not a fixed point and may vary several hundred feet during the cycle of operation, depending upon well conditions.

Two plungers operating in the same eduction tube have an outstanding advantage, as compared to a single plunger device, in increasing the number of loads of well uids delivered to the surface during a 24-hour interval. Smaller loads are raised more frequently with a corresponding improvement in the gas/oil ratio. The quantity of gas required to produce a barrel of Oil is substantially reduced. The elimination of the requirement for a barrier device results in a simplied arrangement of parts and facilitates conversion from a single plunger device to a tandem plunger device.

Accordingly, it is the principal object of this invention to provide a free piston well pump device in which a plurality of valved plungers travel in the same eduction tube, and operate to transfer well uid from a lower plunger to a higher plunger when the plungers meet in physical Contact within the eduction tube.

Another object is to provide a relay `device of this type using two plungers in a single eduction tube, the upper plunger being the same as that used in a single plunger device and the lower plunger having means provided whereby contact between the plungers serves to open the valve in the lower plunger.

Another object is to provide improved means for maintaining the upper plunger at the Well head until the lower plunger has reached the lower end of the eduction tube.

rates Patent ICC Other related and more detailed objects and advantages will appear hereinafter.

In the drawings:

Figure la is a side elevation partly broken away showing a well head installation embodying my invention.

Figure 1b is a longitudinal section view forming a continuation of the lower end of Figure la and shows the lower portion of the eduction tube and the lower plunger resting on the foot piece or bumper device.

Figure 2 is a diagrammatic illustration of the control valve and Well head connections for regulating the ow of uid from the well.

Figure 3 is a longitudinal section view showing the construction of the upper plunger.

Figure 4 is a longitudinal section view showing the construction of the lower plunger.

Figure 5 is a sectional view taken substantially on lines 5--5 as shown on Figure 1a.

Figure 6 is a sectional view taken substantially on lines 6 6 as shown on Figure 5.

Figure 7 is a sectional view taken substantially on lines 7 7 as shown on Figure 3.

Figures 8, 9, l0, and 11, are diagrammatic illustrations showing the operation of a preferred form of my invention.

Figure 12a is a sectional elevation of a modied form of this invention and showing a portion of the well head assembly.

Figure 12b is a section view constituting a continuation of the lower end of Figure 12a.

Figure 13 is a sectional elevation showing details of construction of the latch operating mechanism.

Figure 14 is a sectional elevation taken substantially on the lines 14-14 as shown in Figure 13.

Figure 15 is a transverse sectional plan view taken substantially on the lines 15--15 as shown in Figure 13.

Figure 16 is a fragmentary detail taken substantially on the lines 16-16 as shown in Figure 14.

Referring to the drawings:

The well head assembly generally designated i0 is mounted at the upper end of the well casing 11. The sectional eduction tube 12 extends within the casing 11 and also terminates at the well head assembly le. The eduction tube 12 communicates with a longitudinal bore 13 in the housing 14 by way of the shutoff valve 15 and connecting nipple 16. At the lower end of the eduction tube 12 is mounted a removable bumper assembly 'l which includes a spring 1S and a bumper pad 19.

A pair of plungers 20 and 21 are mounted to travel freely within the same eduction tube l2. 'he upper plunger 26 is substantially the same as that shown in the Knox et al. Patent No. 2,642,002 and is provided with a tubular body 22 having a central passageway 23 extending axially therethrough. Axially spaced sealing assemblies 24 are mounted on the tubular body 22 and each of these sealing assemblies includes radially movable parts which act to form a seal between the body and the interior of the eduction tube 12. A valve generally designated 25 is mounted on the body 22 and serves to block` the passageway 23 when closed. The valve 25 is provided with a head 26 having a frustroconical surface 27. The surface 27 is engageable with the seat 28 formed on the sleeve 29. This sleeve 29 functions as a part of the body 22. The stem 30 of the valve is guided for sliding movement within the bore 31 of the bushing 32, which is fixed to the lower end of the sleeve 29. When the valve 25 is in open position, the valve head 26 rests on the ring magnet 33 and establishes communication between the passageway 23 and the annular space 34 around the sleeve 29 through lateral ports 35. The lower end 36 of the valve stem projectsbelow the lower end of the plunger 20.

The lower plunger 21 is similar in many respects Vto the upper plunger 20. The body 22a has a central passageway 23a closed by the valve 25a. The surface 27a of the valve head 26a closes against the seat 28a. The ring magnet 33a 4acts to hold the valve in open position. The sealing assemblies 24a have sliding contact with the inside surface of the eduction tube 12.

- The lower plunger 21 differs from the upper plunger in that it includes a valve-opening rod 40, which is slidably mounted in guide bearings 41 and 42 and extends axially within the passageway 23a. The bearing 41 is formed by the bore of the body extension 43, and this bore receives the outer cylindrical surface of the cap 44 in sliding relationship. The cap 44 has a bore 44a which slidably receives the bushing 45. This bushing 45 is pinned to the upper end of the rod 40 and is engaged bythe compression spring 46. The bushing 45 rests on the nut 47, which is threaded into the lower end of the cap 44. From this description it will be understood that rod `40 and cap 44 normally move as a unit; upward movement is limited by engagement of the nut 47 with the abutment 48, and downward movement is limited by engagement of the shoulders 49 on the cap 44 and body extension 43.

When the valve surface 27a is closed against the seat 28a and held in that position by differential pressure, the lower end of the rod 40 is engaged by the valve head 26a, and the rod 40 is thus held in an elevated position with respect to the body 22a, the cap 44 projecting well above the top of the body extension 43, and the shoulders 49 being separated. When the upper projecting end S of the cap 44 is engaged by the lower end 36 of the valve 25 on the upper plunger 20, the force is transmitted through the spring 46 to the rod 40. The spring 46 constitutes a force-transmitting element. The rod 40 moves downward relative to the body 22a and mechanically opens the valve 25a.v It will thus be apparent that contact between the plungers serves to close the valve 25 on the upper plunger 20 and open the valve 25a on the lower plunger 21.

The construction of the housing 14 and its associated parts may be substantially the same as that disclosed in the Spalding application Serial No. 349,513 iiled April 17, 1953, now Patent No. 2,757,614.

As shown in the drawings, the spear 51 projects downward through the central cavity 13 in the housing 14. A ange 53 formed integrally with the spear 51 rests on a shoulder 54 which defines the lower end of the counterbore 55. A spring 56 in this counterbore acts to hold the flange 53 against the shoulder 54. A guide bushing 57 is mounted at the other end of the spring and is provided with a central opening 58 which slidably receives the spear extension 59. A removable cap 60 is mounted at the upper end of the housing 14. When the upper plunger 20 enters the central cavity 13, the lower end 62 of the spear 51 projects downward through the central passage 23 in the plunger 20 and engages the valve head 26 to move it to open position. The upper end of the plunger 2li strikes the lower side of the flange 53 after the valve 25 is open. The spring 56 cushions the shock in bringing the plunger 20 to rest within the housing 14. The well fluid raised by the plunger 20 passes out through the flow pipe 63 and through the flow bean 78 and control valve 64.

The spear 51 is provided with a lateral enlargement 65 which forms a restriction 66 within the longitudinal passage 23 in the upper plunger 20. The effect of this restriction 66 is to apply an upward force to the plunger 20 so long as gas passes through the restriction. In this way, the plunger 20 is held within the housing 14 for the required time interval and is prevented from dropping out of the housing under the force of gravity.

Means are provided for initiating closing movement of control valve 64 when the upper plunger 20 enters the housing 14. As shown in the drawings, this means -includes the trigger 67 which is mounted on pivot shaft 68 carried -by-the block 69. `A spring. 70 acts to move'the trigger in a counter-clockwise direction about the shaft 68, as viewed in Figure la. A stop element 71 on the block 69 limits pivotal movement of the trigger 67 under action of the spring 70. A lever 72 xed relative to the shaft 68 normally acts to hold the valve element 73 against the seat 74 thereby preventing escape of gas from the line 75. When the body 22 of the upper plunger 20 strikes the trigger 67, it causes the trigger to move in a clockwise direction as viewed in Figure la thereby moving the plate 72 away from the valve element 73. The valve element in turn moves away from its seat 74 thereby venting the line 75 to atmosphere through the port 76. The shape of the forward face 77 of the trigger 67 is such as to avoid interfering with longitudinal movement of the upper plunger 20 within the central bore 13.

In the general scheme of operationas best shown diagrammatically in Figures 8, 9, l0 and 1l, the upper plunger 20 drops downward through the eduction tube 12, its valve 2S being open. The lower plunger 21 which has been resting on the bumper assembly 17 moves upward, carrying a load of well iiuid labove it. Gas within the casing 11 enters the lower end of the eduction tube through the perforated pipe 61. Since the valve 25a is closed, this gas pressure lifts the lower plunger 21 and its load of well fluid.

Figure 9 shows the lower plunger 21 moving upward and the upper plunger 20 moving downward. The upper plunger 20 drops through the well uid being raised by the lower plunger 21, the well uid passing through the open valve 25 and through the central passage 23 into the space above the upper plunger 20.

Figure 10 shows the plungers meeting at some point approximately midway between the top and bottom of the eduction tube 12. The lower end of the valve 25 on the upper plunger 20 strikes the upper end 50 of the rod element 40 on the lower plunger 21. This action serves to close the valve 25 on the upper plunger and to open the valve 25a on the lower plunger. Both plungers then reverse direction.

As shown in Figure 1l, the lower plunger 21 drops back down the eduction tube 12 and through the column of well fluid which has accumulated in the lower end of the eduction tube. The valve 25a does not close until the lower end thereof strikes the bumper pad assembly 17. The upper plunger 20 continues moving upward in the eduction tube 12, its valve 25 remaining closed. The load of well iiuid passes out through the well head and liow pipe 63. Just before the upper end of the plunger 20 strikes the ange 53 the spear 51 opens the valve 25. The upper plunger 20 does not immediately drop by gravity however, because gas flowing through the passage 23 passes through the restriction 66 imposed by the enlargement 65 on the spear 51. The resulting pressure drop across the plunger 20 hold its against the flange 53 when the control valve 64 (see Figure 2) begins to close. The reduction in rate of ow of gas through the passage 23 reduces the force to a value insucient to maintain the plunger 20 against the force of gravity, and accordingly the plunger 20 drops down through the eduction tube away from the well head. The speed of descent of the plungers 20 and 21 may be retarded by means of the removable choke rings 52 and 52a mounted on the bushings 32 and 32a. Choke rings of different sizes may be used to vary the speed of descent, since it is highly desirable that the plungers 20 and 21 fall at approximately the same speed.

The control instrument, generally designated 79, vordinarily is not required for operating the plungers 20 and 21. The trigger pipe 75 is connected directly to the control line 91. Both of these lines receive gas under pressure from the pilot supply line via the restricted orice 85a.

p When the vent valve 73 opens'so that the trigger pipe 75 pressure in the upper portion of the diaphragm chamber 130 is likewise reduced and the valve spring 131 moves the stem 124 upward to close the valve 64. The rate of closing of the valve 64 is regulated by the force of the check valve spring 132. The valve 64 closes slowly, and when the rate of flow of gas through it falls below a predetermined magnitude, the upper plunger 20 drops out of the well head and falls by gravity down through the eduction tube 12. When the upper plunger 20 leaves the housing 14, the spring 70 returns the trigger 67 to its initial position against the stop 71. The arm 72 moves the valve 73 against the seat 74, thereby preventing further escape of gas from trigger pipe 75 to the vent port 76. Pressure being supplied from the pilot supply line 85 builds up pressure in the trigger pipe 75 and in the control line 91. This pressure applied to the oil dash pot 127 causes oil to ow through the adjustable orifice 12S and into the chamber above the diaphragm 92. The rate of opening of the valve 64 is determined by the setting of the adjustable orice 128.

From the above description it will be understood that the plungers 20 and 21 operate on their own time cycle without regulation of any timing clock and without regulation based on casing pressure.

In the modied form of this invention, there is provided mechanical latch means for maintaining the upper plunger within the well head for the desired time interval. This form of my invention is shown in Figures 12a-16 and it uses the control instrument shown in Figure 2, and generally designated 79. In this form of my invention, the upper and lower plungers do not operate on their own time cycle but on the contrary the motion of the plungers is regulated by the control instrument 79 and is dependent on changes in pressure within the casing 11.

In this modified form of my invention the upper and lower plungers are substantial duplicates. Each includes a body 22h having a central axial passage 23h. A valve generally designated 2517 is mounted near the lower end of the body to close for the longitudinal passage 23h. This vve is similar to that previously described and includes a head 26h having a frusto-conical surface 27h which Closes against the seal 2817. The valve stem 36h projects downward below the lower end of the plunger bushing 32h. Sealing assemblies 24h engage the inner surface of the eduction tube 12.

Each of the plungers has an axially extending rod 4Gb for opening the valve 2517. This rod 4Gb and its associated cap 44h are constructed in substantially the same manner previously described in connection with the lower plunger 21.

The annular shoulder 133 on the body extension 43b is engaged by a pivot latch 134 mounted on the bumper 'block 135 within the housing 14h. A pin 136 lixed on this bumper block travels in the axial keyway 137 provided in the housing 14h. The bumper block is carried on the lower end of the stem 138 which projects through the opening 139 in the sleeve 140. The shoulder 141 on the sleeve receives one end of the compression spring 142. The other end lof the spring engages the threaded cap 143 on the housing 14h. A smaller spring 144 supports the stem 133 on the sleeve 140 by means of the washer 145 and nut 146. Well uid raised by the upper plunger Ztlb passes through ports 147 in the sleeve 140 and out through the ow pipe 63b.

The latch 134 is connected to the bumper block 135 by means of the pivot pin 148. A spring 149 acts to maintain the latch 134 in engagement with the shoulder 133. Means are provided for -tripping the latch 134 and as shown in Figures l3-l6, this means includes a pneumatic device generally designated 150 acting through a shaft assembly 151 to operate the radially movable pin 152. The block 153 is secured to the housing 14h by means of threaded elements 154. A vertical shaft 155 is mounted to turn in the block 153. This shaft carries an arm 156 at its upper end arranged to contact the pin 152. A spring 157 maintains the pin in contact with the arm 156. The shaft 155 extends through bushing 158 and has a clutch part 159 fixed thereto. A mating clutch part 165) is mounted to turn on the shaft 155 and a spring 161 holds the clutch parts in engagement. A11 arm 162 on the clutch part 160 is positioned to be engaged by the end of the rod 163. This rod is connected to the bellows 164 by means of the cup-shaped ilange element 165. A spring 166 normally acts to retract the rod 163 from contact with the arm 162. A casing 167 encloses the bellows 164 and defines a pressure chamber 168 outside the bellows. When this chamber 168 is pressurized from the conduit 169 the bellows are compressed causing the rod 163 to move in a direction to compress the spring 166. From this description it will be understood that when pressure is applied through line 169, the shaft 155 is turned in a direction to cause the pin 152 to move radially inward. This action swings the latch 134 in a counter-clockwise direction as viewed in Figure 12a with the result that the upper plunger Ztib is free to fall by gravity out of the well head and down through the eduction tube.

1n the operation of this modied form of the invention the upper and lower plungers function in substantially the same manner as shown diagrammatically in Figures 8, 9, l0, and l1. lThe principal difference is that the plungers are duplicates and the upper plunger is mechanically latched at the well head until opening movement of the control valve 64 is initiated. The trigger 67b and associated parts operate to bleed the pipe 75 to atmosphere when the upper plunger 20h enters the housing 1417, as previously described.

in order to carry out the cycle of operation for this modified form of my invention, there is provided control mechanism which causes the valve `64 to open when the casing pressure rises to a predetermined magnitude, and which causes the valve 64 to close when the upper plunger Ztlb enters the housing 14. A preferred form of control mechanism is shown diagrammatically in Figure 2. This mechanism is similar to that shown in the Tait Patent No. 2,649,738 granted August 25, 1953. In this modilied form of my invention, the trigger pipe 75 no `longer lconnects directly to the control line 91, and the line containing the orifice a is omitted. Pipe connections are shown by the phantom lines.

As shown in Figure 2, the control instrument generally designated 79 comprises a casing having a number of parts of the control mechanism positioned therein. Among these parts are the pilot valve S0, the relay valve S1, the bellows assembly 82, the Bourdon tube 83 and the valve assembly 84. Pilot supply gas at relatively low pressure, for example 2O p. s. i., is supplied through conduit 85 to the terminal S6 of the relay valve 81 and to the terminal 37 of the pilot valve Si). This pilot supply gas may be obtained from any convenient source, and as shown in Figure 2 is obtained through a pressure reducing regulator 88 connected to the gas supply pipe 89. The line is connected to the supply pipe 89 at a point near to the entrance to the casing 11 and hence reflects the pressure therein. This line 90 is connected tothe Bourdon tube 83.

The control line 91 communicates with the space above the diaphragm 92 of the control valve 64 and this control line also connects to the terminal 93 of the pilot valve S0 and to the terminal 94 of the bellows assembly 82. The trigger line 75 connects to the valve assembly 34 and to the terminals 95 and 96 of the relay valve 81. The terminal 97 on the pilot valve S@ connects through line 93 to the terminal 99 on the relay valve 31.

The relay valve 81 employs a ball 100 which may engage an upper facing seat 1il1 or a downward facing seat 162. When the ball 161) falls by gravity on the seat 101, it closes off the vent port 103. A diaphragm 104 operates a plunger which may engage the ball 100 7 and move it upward away from seat 101 and into contact 'with seat 102. Pressure fluid admitted through terminal 96 operates the diaphragm 104. A restriction 106, located for convenience within the relay valve 81 connects terminals 86 and 95 and hence establishes communication between the pressure uid supply line 85 and the trigger line 75. The pilot valve shown diagrammatically at 93 is provided with a valve spool 107 which moves axially within a cylindrical bore 108. An annular groove 109 in the spool 107 connects the terminal 93 with either the terminal 87 or the vent port 110, depending upon the axial position of the spool 107. A compression spring 111 acts resiliently to move the spool 107 in one direction and such movement is resisted by iluid pressure in the chamber 112 below the spool 107.

The Bourdon tube 83 has its moving end connected to the crank arm 113 of the apper valve 114. The flapper valve is pivotally mounted at 115. A nozzle 116 engages the underside of the apper valve 114 to form a seal. The nozzle 116 is also movably mounted, and as shown diagrammatically in the drawings, the nozzle is carried on an arm 117 pivotally supported at 118. A link 119 is pivoted at one end to the arm 117 and at the other end to the post 120 fixed on the end wall of the bellows 82. When the pressure in the bellows chamber 121 increases, the nozzle 116 is moved toward the apper valve 114. One or more loops 122 in the nozzle feed pipe 123 permit the nozzle 116 to move freely through its relatively short arc of movement. When pressure in the Bourdon tube 83 increases, the flapper valve 114 is swung toward the nozzle 116. The nozzle 116 and apper valve 114 are collectively referred to as the vent valve 84. Y

In the position of the parts as shown in Figure 2, the

trigger line 75 is pressurized and the vent valve 84 is closed. A release in pressure below the diaphragm 104 in the relay valve 81 allows the sliding post 105 to drop, and the ball 100 then rests on seat 101, closing or'r` vent port 103. Pressure from the pilot supply line 85 then passes into the relay valve 81 through terminal 86, out through terminal 99, through pipe 98 and into the chamber 112 in the pilot valve 80 through terminal 97. The spool 107 moves upward against the action of the spring 111 to close oi terminal 87 and to connect the terminal 93 with the vent port 110. The control pipe 91 is then vented to atmosphere, and the reduction in pressure in the space above the diaphragm 92 of the control valve 64 permits the spring to lift the valve stem 124 to close valve heads 125 against the valve seats 126. Venting of the control pipe 91 through vent port 110 in pilot valve 80 serves to effect closing of the control valve 64, as set forth above, and also acts to decrease the pressure in the bellows chamber 121. This pressure decrease allows the arm 117 to swing about its pivot 118 and move the nozzle 116 away from the apper valve 114. The nozzle 116 then vents the line 123 and trigger pipe 113 to atmosphere even though pressure uid is being constantly supplied through restriction 106 from pilot supply pipe 85. A reduction in casing pressure is occasioned by ilow of gas through the control Valve 64 during the period that it is open. This reduction in pressure is reflected by action of the Bourdon tube in lifting-the tlapper valve 114 away from the nozzle 116. The control valve 64 remains closed with the` well shut 1n.

The lower plunger remains at the lower end of the eduction tube 12 until the pressure in the casing 11 builds up to a predetermined value. The Bourdon tube 83 then acts to swing the apper valve 114 in a clockwise direction as viewed in Figure 2 to seat against the nozzle 116 and thereby substantially prevent escape of pressure iiuid therefrom. Pressure uid supplied through restriction 106 then builds up pressure in the line 123 iand trigger pipe 75. The diaphragm 104 in the relay valve 81 is raised, Vcausing the post 105 tol seat-the ball against the seat 102. This action vents line 98 through port 103 and allows the spring V111 in the pilot valve 80 to shift the spool 107 to a position toy close off the vent port and to connect terminal 87 with terminal 93. 'Pressure fluid then passes from pilot supply line '85 into the control pipe 91, and into vthe bellows chamber 121.

When pressure in the control pipe 91 builds up suciently, it acts via the oil dash pot 127 and adjustable orifice 128 to apply a force to the upper side of the diaphragm 92, This serves to overcome the force of the spring and to move the valve stem 123 downward to open the control valve 64. Gas under pressure in the eduction tube 12 then passes out through the flow pipe 63. The consequent reduction of pressure in the eduction tube 12 below the lower plunger causes the lower plunger to be driven upward by gas pressure, carrying a load of well uid above it.

From the above description it will be understood that the control instrument 79 serves to initiate opening movement of control valve 64 when pressure in the casing 11 reaches a predetermined magnitude. The control valve 64 begins closing when the upper plunger 20b strikes the trigger 67b in the housing 14b.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth but my invention is of the full scope of the appended claims.

I claim:

l. For use with an eduction tube extending into a well, a pair `of valved plungers each slidably engaging the inside surface of the eduction tube for longitudinal movement therein, the plungers being capable lof meeting in contact at diierent locations axially of the eduction tube, and means on the plungers whereby contact between the plungers is eective to open the valve on the lower plunger and to close the valve on the upper plunger.

2. For use with an eduction tube extending into a well, a pair `of valved plungers each-slidably engaging the inside surface of the eduction tube for longitudinal movement therein, the plungers being capable of meeting in contact at different locations axially of the reduction tube, each of the plungers having a body provided with a longitudinal passage and a Valve for closing the passage, and means on Ithe plungers whereby contact between the plungers is effective to open the valve on the lower plunger and to close the valve on the upper plunger.

3. A free piston well pump device, comprising in combination: a `sectional eduction tube extending intoa well, upper and lower plungers each slidably engagingthe inside surface of the eduction tube for longitudinal movement therein, the plungers being capable of meeting in `contact at different locations axially of the eduction tube, each of the plungers having a body provided with a longitudinal passage and a valve for closing the passage, and means on the plungers whereby contact between the plungers is effective to open the valve von the lower plunger and to close the valve on the upper plunger.

4. For use with an eduction tube extending into a well, the combination of: a plunger having a body provided with a longitudinal passage including a cylindrical bore, a valve mounted on the body for closing the passage, means at the upper end of the eduction tube for mechanically opening the valve, said means including -a spear adapted to extend into said passage, and an enlargement on the spear intermediate the ends thereof and adapted to form a restriction with said cylindrical bore.

5. A free piston well pump device including a educ- .tion tube extending into a well, a pair 'of valved plungers each slidably engaging the inside surface ofthe tube for longitudinal movement therein, the plungers being vcapable of meeting in contact at different locations axially of the eduction tube, each plunger having a longitudinal `passage and a valvefor closing the passage, means at the upper end of the eduction tube for mechanically opening the valve on the upper plunger, said means including a spear adapted to extend into the passage in the upper plunger, an enlargement on the spear forming a restriction within said passage, and means whereby contact between the plungers is effective to open the valve on the lower plunger and to close the valve on the upper plunger.

6. Multiple stage free piston well pump apparatus having in combination: an eduction tube, a well head assembly at the upper end of the eduction tube, a flow pipe extending from the well head assembly, a control valve for regulating flow in the flow pipe, a pair of valved plungers traveling freely in sliding contact with the eduction tube, the plungers being capable of meeting in Contact at different locations axially of the eduction tube, each plunger being tubular and having a valve adapted to move upwardly thereon toward closed position, means on the plungers whereby contact between the plungers serves to close the valve on .the upper plunger and open the valve on the lower plunger, pneumatic means including a pressurized control line for opening the :control valve, resilient means opposing the action of the pneumatic means, and trigger means on the well head assembly engageable by the upper plunger and operable to vent the control line to render the pneumatic means ineffective, whereby the resilient means may close the control valve.

7. Multiple stage free piston well pump apparatus having in combination: an eduction tube, a well head assembly at the upper end of the eduction tube, a bumper assembly at the lower end thereof, a pair of valved plungers traveling freely in contact with `the inside surface of the eduction tube, the plungers being capable of meeting in contact at different locations axially of the eduction tube, each plunger having a longitudinal passage and having a valve for closing the passage, and means whereby contact between the plungers serves to close the valve on the upper plunger and open the valve on the lower plunger, whereby well fluid raised by the lower plunger for a substantial distance in the eduction tube may be transferred to the upper plunger and lifted thereby to the well head assembly.

8. Multiple stage free piston well pump apparatus having in combination: an eduction tube, a well head assembly at the upper end of the eduction tube, a valved lunger traveling freely within the eduction tube, the plunger being tubular and having a valve adapted to move upwardly toward closed position, mechanical latch means on the well head assembly engageable with the plunger to prevent its descent, a flow pipe extending from the well head assembly, a control valve for regulating flow in the flow pipe, and common means for releasing the latch and for initiating closing movement of the control valve.

9. Multiple stage free piston well pump apparatus having in combination: an eduction tube, a well head assembly at the upper end of the eduction tube, a pair of valved plungers traveling freely within the eduction tube, each plunger being tubular and having a valve adapted to move upwardly toward closed position, mechanical latch means on the Well head assembly engageable with the upper plunger, a flow pipe extending from the well head assembly, a control valve for regulating flow into the flow pipe, common means for releasing the latch and for initiating closing movement of the control valve, and means whereby .contact between the plungers serves to close the valve on the upper plunger and open the valve on the lower plunger.

l0. Multiple stage free piston well pump apparatus, having in combination: an eduction tube extending into a well, a pair of valved plungers traveling freely within said eduction tube, each of the plungers being tubular and each having a valve adapted to move upwardly to- Ward closed position, mechanical latch means mounted 1i) at the upper end of the eduction tube and engageable with the upper plunger, and means including an actuating element longitudinally movable on the lower plunger adapted to be contacted by a portion of the valve on the upper plunger, the actuating element being movable to open the valve on the lower plunger.

ll. Multiple stage free piston well pump apparatus having in combination: an eduction tube extending into a well, a well head assembly at the upper end of the eduction tube, a pair of duplicate valved plungers traveling freely within said eduction tube, each of the plungers being tubular and each having a valve adapted to move upwardly toward closed position, a rod element longitudinally movable :on each plunger and adapted to open the valve thereon, the rod element projecting from the upper end of each plunger, mechanical latch means on the well head assembly engageable with the upper plunger, the rod element on the upper plunger being engageable with a part on the well head assembly to open the valve on the upper plunger, and the rod element on the lower plunger being engageable with a valve part on the upper plunger to open the valve on the lower plunger.

l2. For use with an eduction tube extending into a well, a pair of valved plungers each slidably engaging the inside surface of the eduction tube for longitudinal movement therein, means whereby Contact between the plungers is effective to open the valve on the lower plunger and to close the valve on the upper plunger, and a choke ring on each plunger for regulating the speed of descent thereof.

i3. For use with an eduction tube extending from the ground surface into a well, a pair of plungers each slidably engaging the inside surface of the eduction tube for longitudinal movement in opposite directions, each plunger having a valve thereon, the upper plunger being adapted to reciprocate in the upper portion of the eduction tube and the lower plunger being adapted to reciprocate in the lower portion thereof, each of the plungers being movable into the range of travel of the other so that they are capable of meeting in contact at different locations axially of the eduction tube, means at the upper end of the eduction tube engaged by the upper plunger to open the valve thereon, means at the lower end of the eduction tube engaged by the lower plunger to close the valve thereon, and means on the plungers whereby contact between them is eective to open the valve on the lower plunger and to close the valve on the upper plunger.

14. For use with an eduction tube extending from the ground surface into a well, an upper plunger adapted to reciprocate in the upper portion of the eduction tube and capable of traveling more than one-half of the length thereof while contacting the inner surface thereof, a lower plunger adapted to reciprocate in the lower portion of the eduction tube and capable of traveling more than one-half the length thereof, while contacting the.- inner surface thereof, the plungers being capable of meeting in contact at different locations axially of the eduction tube, each of the plungers having a valve thereon, means at the upper end of the eduction tube engaged by the upper plunger to open the valve thereon, means at the lower end of the eduction tube engaged by the lower plunger to close the valve thereon, and means on the plungers whereby Contact between them is effective to open the valve on the lower plunger and to close the valve on the upper plunger.

References Cited in the le of this patent UNITED STATES PATENTS 2,246,577 Davis June 24, 1941 2,508,174 Knox et al May 16, 1950 2,649,738 Tait Aug. 25, 1953 2,676,547 Knox Apr. 27, 1954 2,699,121 KnOX lan. 11, 1955 

